1. Field of the Invention
The present invention relates to a CF (coated front) formulation for carbonless copy paper. The invention further relates to a coated front (CF) for carbonless copy paper for use in magnetic image character recognition (MICR) applications. More particularly, the invention relates to an improved CF formulation for carbonless copy paper for use in MICR applications, the formulation containing a zincated phenolic resin and a latex binder.
2. Description of the Prior Art
In the preparation of carbonless copy paper a layer of pressure rupturable colorless dye precursor is coated on the underside or backside of a top sheet, which layer is referred to as a coated back or (CB) layer. This top sheet is mated with a bottom sheet which contains a coating with a dye acceptor for the dye precursor, which coating is referred to as a coated front or (CF) layer. To develop a color image pressure is applied to the top sheet to rupture the microcapsules on the back thereof. This releases the microcapasule contents, a fluid containing dissolved colorless dye precursor. The released capsule contents, dye precursor with fluid, contacts the dye acceptor in the CF layer thereby developing a color image. Multiple copies may be made by the addition of intermediate sheets, referred to as (CFB), which contain both coated front layers, (CF) and coated back layers, (CB).
Prior art MICR coded carbonless copy paper provided significant problems to consumers when used with their sorting equipment. Standard CF has, as the coating adhesive, either a starch only binder system or a binder system containing insufficient latex to be useful in MICR applications. Starch lacks the flexibility and durability needed to withstand the MICR crash imprinting process.
When a standard CF is used for MICR applications, such as when MICR characters are printed onto CF checks or CF tickets using a "crash imprint" numbering head, the equipment, in common use, stresses the CF surface during the imprint process. Prior art solutions to this problem have included printing the CF coating only in those areas which will not receive MICR printing. When using a full coat standard CF product, the inked area of impact may flake loose in spots (e.g. tiny areas of specific numbers or other characters). This flaking may happen immediately during the printing process or later on during use. When voids caused by CF failure occur in the printed characters, errors take place in the end users' equipment. The magnetic image character recognition (MICR) scanner is not able to correctly classify the faulty image.
When the MICR character is on a bank check, the check may be put through a sorting process as many as 30 times or more. If the character is not clearly defined throughout the lifetime of use of the check, sorting errors occur. Sorting errors are usually corrected by hand, are time consuming and costly to the end user.